Process for manufacturing cold cathode gas discharge devices and the product thereof

ABSTRACT

The invention comprises a process of manufacturing cold cathode gas discharge devices. A unitary metal electrode structure is inserted through a glass support, the metal and glass having the same coefficient of thermal expansion. The support and electrode structure are heated in the presence of oxygen to effect a seal therebetween. The gas discharge device is completed without removing the oxide coating formed on the electrode surfaces of the structure during the heating step. The resulting gas discharge device, which may be used for display purposes, has a stable oxide coating on electrodes thereof that attenuates display distorting reflections.

United States Patent [151 3,697,797 F reyheit et a1. 14 1 Oct. 10, 1972[54] PROCESS FOR MANUFACTURING 3,551,721 12/1970 Holz ..315/169 R X COLDCATHODE GAS DISCHARGE 3,603,837 9/ 1971 Turner ..3 15/ 169 R X DEVICESAND THE PRODUCT THEREOF Primary ExaminerRoy Lake AssistantExaminer-Siegfried H. Grimm [72] Inventors: Paul J. Freyhelt, FrammghamAttorney sl Yeaton Center; Claude D. Lustig, Lexing- 1011, both Of Mass.[73] Assign: Sperry Rand Comm-36 The invention comprises a process ofmanufacturing 22 Filed; Jam 25, 1971 cold cathode gas discharge devices.A unitary metal electrode structure is inserted through a glass support,[211 App! 109371 the metal and glass having the same coefficient ofthermal expansion. The support and electrode struc- 52 us. Cl...313/217, 29/25.!6, 65/154, we are heated in the presence of yg toeffect a 313/109.5, 313/218, 313/221, 313/245 Seal therebetween. The gasdischarge device is [51] Int. Cl ..H0l j l/94, H01 j 9/18, H0 1 j 17/48completed without removing the oxide coating formed [58] Field ofSearch...313/ 188, 109.5, 189, 210, 217, on the electrode surfaces ofthe structure during the 313/218, 221, 244, 245, 283, 356; 315/167,heating step. The resulting gas discharge device, which 169 R, 169 TV,260; 340/324 R, 166 EL; may be used for display purposes, has a stableoxide 65/154; 29/25.15, 25.16 coating on electrodes thereof thatattenuates display distorting reflections. 156] References Cited 9Claims, 2 Drawing Figures UNlTED STATES PATENTS 3,465,194 9/1969 l-lall..313/2l7 X CATHODE GAS DISCHARGE DEVICES AND THE PRODUCT THEREOFBACKGROUND OF THE INVENTION 1 Field of the Invention The presentinvention pertains to the manufacture of cold cathode gas dischargedevices particularly of the type utilized for display purposes.

2. Description of the Prior Art Methods are known in the manufacture ofelectron tube devices, and particularly in the manufacture of ofmanufacturing the devices are often removed to preclude contaminationand hence faulty operation. Although'providing clean electrode surfacesin the resulting devices, this welded construction technique islaborious, time consuming and hence expensive. Furthermore, suchspot-welds are subject to deterioration under the influence ofvibration. Additionally, the step of removing the residual oxidecoatings is undesirable since it further complicates the manufacturingprocedures.

SUMMARY OF THE INVENTION The present invention eliminates the prior artwelded electrode construction as well as any oxide cleaning steprequired in the prior art methods. The present invention utilizes aunitary metal electrode, such as a rod, comprised of a metal having thesame coefficient of thermal expansion as the glass through which theelectrode is to be sealed. The steps of the present invention includeinserting the electrode through a close fitting glass support. Theassembly is heated in the presence of oxygen until the glass softens.Pressure is then applied to squeeze the softened glass against the metalelectrode. Oxide formed on the surfaces of the metal during the heatingstep combines with the softened glass to effect the desired seal. Theoxide coating formed during the heating step is not only beneficial ineffecting a proper glass to metal seal, but it is stable, adherent anddoes not significantly afiect the operation of the assembled devices.The invention eliminates the welded electrode construction and the oxidecleaning steps of the prior art resulting in a substantially moreeconomical manufacturing process while providing devices superior tothose produced by the prior method. a

Additionally, not only does the oxide coating on the electrode surfacesnot interfere with the long lived operation of the devices butthecoating provides an additional beneficial result in devices utilized fordisplay purposes. The oxide coating attenuates reflections from theelectrode surfaces which reflections have heretofore tended to distortthe displayed information.

2 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view,partially in section, of a cold cathode gas discharge display deviceconstructed in accordance with the process of the present invention; and

FIG. 2 is a magnified view of a portion of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Although the present inventionhas applicability in a wide variety of cold cathode gas dischargedevices, the invention will be explained in terms of a gas dischargedisplay device utilizing hollow cathodes. Detailed descriptions of sucha device may be had in copending US. Pat. application Ser. No. 27,608,filed Apr. 13, 1970, entitled Gas Discharge Display Apparatus UtilizingHollow Cathode Light Sources, invented by Claude D. Lustig and assignedto the assignee of the present invention. In particular, the inventionwill be explained in terms of a hollow cathode structure formed of ametal alloy consisting of 49 percent iron and 5 1 percent nickel sealedin a soda-lime glass support. This alloy may be commercially procuredfrom, for example, the Wilbur B. Driver Company as Niron 52. It is knownthat this alloy and soda-lime glass have substantially the samecoefiicient of thermal expansion thereby providing sound glass-to-metalseals over normally encountered temperature ranges.

Referring to FIG. 1, a cold cathode gas discharge display device 10utilizing hollow cathodes is illustrated.

The structure and operation of the device 10 is explained in detail insaid US. Pat. application Ser. No. 27,608 and will be briefly describedhere for completeness. The display device 10 comprises a glass support11 having a matrix of apertures formed therethrough. A hollow cathoderod such as the rod 12 is sealed in each of the apertures of the matrix.A transparent dielectric plate 13 having transparent metal anode strips14 affixed thereto is sealed to the cathode assembly to form a gastightenvelope. Conductors 15 for addressing the cathodes in the mannerdescribed in said US. Pat. application Ser. No. 27,608 are connected tothe cathodes and anodes. The cathode rods, such as the rod 12 arecomprised of a metal alloy consisting of 49 percent iron and 51 percentnickel and the support 11 is comprised of soda-lime glass as previouslymentioned. It is known that a metal alloy having this composition andsoda-lime glass have the same coefiicient of thermal expansion. Thus, aspreviously explained, the seal effected between the rod 12 and the glasssupport 11 is structurally sound over the temperature ranges normallyencountered. A portion 16 of the device 10 including a hollow cathoderod 20 is illustrated in magnified view in FIG. 2.

Referring to FIG. 2, in which like reference numerals indicate likecomponents with respect to FIG. 1, the cathode rod '20 is sealed in anaperture 21 of the glass support 11. The cathode 20 has a hole 22disposed therein, the interior surfaces thereof functioning as thecathodic surfaces of the electrode 20 in the manner described in saidUS. Pat. application Ser. No. 27,608. The cathode rod 20 furtherincludes a rim 23.

The rod 20 is sealed in the aperture 21 by the method of the presentinvention which comprises the following steps: The metal structure 20 isinserted into the aperture 21 in the glass support 11. The assembledstructure is then heated in the presence of oxygen at atemperaturesufficient to soften the glass support 11. Since the heating step isperformed in the presence of oxygen, oxide is formed on all of the innerand outer surfaces of the cathode 20. For example, oxide is formed onthe outer cylindrical surfaces thereof as well as on the inner orcathodic surfaces of the hole 22 and on the l rim 23. Pressure is thenapplied to the softened glass support 11. The oxide formed on theportion of the outer surface of the rod 20 that is inserted in theaperture 21 combines with the softened glass to effect a gastight sealbetween the members 11 and 20. Subsequent to the heating step, thedevice 10 (FIG. 1) is assembled, as described in said US. Pat.application Ser. No. 27,608 without removing the oxide coating formed onthe rim 23 and the cathodic surfaces of the hole 22. The oxide formed asdescribed above has a mat black surface, is of stable composition and ishighly adherent to the surfaces of the cathode rod 20. It is to be notedwith respect to FIGS. 1 and 2 that the black oxide coating on thecathodic surfaces of the hole 22 and on the rim 23 is depicted bystippling where clarity is enhanced.

It will be appreciated that the heating step in the presence of oxygenmay be performed with the device exposed to the atmosphere whichprovides the oxygen required to effect the glass-to-metal seal. A glasssoftening temperature found suitable for the heating step with respectto the above-discussed materials is approximately l,0O C.

Display devices of the type illustrated in FIG. 1 have been operated athigh current densities for extended periods without any significantchange in the operating conditions thereof. Such changes would have beenapparent if there had been any significant degradation in gascomposition or cathodic surfaces.

From the foregoing, it is appreciated that significant manufacturingeconomies are realized in practicing the method of the present inventionsince the step conventionally performed of spot welding electrodes iseliminated and no steps are necessary to remove the residual oxidecoating from the cathodic surfaces. These economies are particularlysignificant with regard to the gas discharge devices of the typediscussed above and in said US. Pat. application Ser. No. 27,608 becauseof the complex contours of the cathodic surfaces of the hollow cathodes.

Additionally, the method of the present invention provides novel displaydevices whose glowing cathodes generate the display information. Theseglowing cathodes are uniquely coated with a stable mat black oxide thatis effective in attenuating display distorting reflections while notimpairing the normal operation of the device.

, It will be appreciated that the invention comprising the use of asingle metal piece to provide both the cathodic surface and theglass-metal seal, such metal piece not requiring cleaning to removeoxide depositions, is applicable also-to devices where the glassmetalseal is accomplished at much lower temperatures by the use of a glassfrit.

While the invention has been described in its preferred embodiment, itis to be understood that the words which have been used are words ofdescription rather than limitation and that changes may be made withinthe purview of the appended claims without departing from the true scopeand spirit of the invention in its broader aspects.

We claim: 1. In a process for manufacturing cold cathode gas dischargedevices comprising the steps of inserting a metal electrode structureinto a glass support, said metal and said glass having the samecoefiicient of thermal expansion,

heating said support and electrode structure in the presence of oxygenat a softening temperature of said glass to effect a seal therebetween,and a inserting a metal alloy electrode structure into a glass saidalloy consisting of approximately 49 percent iron and 51 percent nickel,

said glass having the same coefficient of thermal expansion as saidalloy,

heating said support and electrode structure in the presence of oxygenat a softening temperature of said glass to effect a seal therebetween,and

completing said devices without removing the oxide coating formed on theelectrode surfaces of said structure during said heating step.

3. In a process for manufacturing cold cathode gas discharge devicescomprising the steps of inserting a metal alloy cathode rod through aglass support,

said alloy consisting of approximately 49 percent lime glass support,said alloy consisting of approximately 49 percent iron and 51 percentnickel,

heating said support and cathode rod in the presence of oxygen at asoftening temperature of said glass to effect a seal therebetween, and

completing said devices without removing the oxide coating formed on thecathodic surfaces of said structure during said heating step.

5. In a cold cathode gas discharge display device glass support means,and

metal electrode means sealed in said support means,

the electrode surfaces of said electrode means being coated with anon-reflective oxide formed thereon by heating in the presence of oxygenthereby attenuating display distorting reflections from said surfaces.

6. In the device of claim 5 in which said surfaces comprise the cathodicsurfaces of said cathode means.

8. In the device of claim 7 in which said cathode means comprises aunitary piece of said alloy, a portion thereof being sealed to saidglass and another portion thereof forming said cathodic surfaces.

9. In the device of claim 7 in which said cathode means comprises a rodof said alloy.

2. In a process for manufacturing cold cathode gas discharge devicescomprising thE steps of inserting a metal alloy electrode structure intoa glass support, said alloy consisting of approximately 49 percent ironand 51 percent nickel, said glass having the same coefficient of thermalexpansion as said alloy, heating said support and electrode structure inthe presence of oxygen at a softening temperature of said glass toeffect a seal therebetween, and completing said devices without removingthe oxide coating formed on the electrode surfaces of said structureduring said heating step.
 3. In a process for manufacturing cold cathodegas discharge devices comprising the steps of inserting a metal alloycathode rod through a glass support, said alloy consisting ofapproximately 49 percent iron and 51 percent nickel, said glass havingthe same coefficient of thermal expansion as said alloy, heating saidsupport and cathode rod in the presence of oxygen at a softeningtemperature of said glass to effect a seal therebetween, and completingsaid devices without removing the oxide coating formed on the cathodicsurfaces of said rod during said heating step.
 4. In a process formanufacturing cold cathode gas discharge devices comprising the steps ofinserting a metal alloy cathode rod through a soda-lime glass support,said alloy consisting of approximately 49 percent iron and 51 percentnickel, heating said support and cathode rod in the presence of oxygenat a softening temperature of said glass to effect a seal therebetween,and completing said devices without removing the oxide coating formed onthe cathodic surfaces of said structure during said heating step.
 5. Ina cold cathode gas discharge display device glass support means, andmetal electrode means sealed in said support means, the electrodesurfaces of said electrode means being coated with a non-reflectiveoxide formed thereon by heating in the presence of oxygen therebyattenuating display distorting reflections from said surfaces.
 6. In thedevice of claim 5 in which said metal comprises an alloy consisting ofapproximately 49 percent iron and 51 percent nickel, said oxidecomprises a mat black oxide formed on said surfaces by heating in thepresence of oxygen at a softening temperatures of said glass, and saidglass has the same coefficient of thermal expansion as said alloy.
 7. Inthe device of claim 6 in which said glass comprises soda-lime glass,said electrode means comprises cathode means, and said surfaces comprisethe cathodic surfaces of said cathode means.
 8. In the device of claim 7in which said cathode means comprises a unitary piece of said alloy, aportion thereof being sealed to said glass and another portion thereofforming said cathodic surfaces.
 9. In the device of claim 7 in whichsaid cathode means comprises a rod of said alloy.